Bread is one of the most basic foods we eat and is a symbol of many different ideas.
When Asagi christens Beneatha as "Alaiyo" or "one for whom bread – food – is not enough", it is truly an apt description of her character. Bread used to be the staple food in the diets of ancient civilizations and because of this bread can be interpreted as a symbol of substance or life. So, Asagi essentially describes Beneatha as someone for whom life by itself is not satisfying enough. This is true because she is always questioning her surroundings, and she constantly changes from hobby to hobby such as horseback riding, acting lessons, and guitar lessons. This shows Asagi's high opinion of her because he believes that she is an intellectual person just like him and this is why he is attracted to her. Her journey of fulfillment and self-expression is mocked by others in the family, but she still wants to broaden her mind.
In the Bible, bread is also used to symbolize a financial investment. This correlates to Walter because he wants to invest in a liquor store that he believes will bring money to the family. The other side of Beneatha's nickname is that it also applies to Walter because he is also not satisfied by his life and he wants to be more successful. For both of them, their bread is their way of life or the ghetto. Since they are both not satisfied with this, they want to use the check to escape their current lives and to explore the world further. Thus, the nickname given by Asagi shows how Walter and Beneath are simply two sides of the same coin.